Field of the Invention
The present invention relates to a fluid-filled, frequency-dependent damper, comprising a cylinder connected to a cylinder attachment portion; a piston connected to a piston attachment portion, the piston being displaceable in the cylinder; a first main chamber; a second main chamber; and a throttling member constructed and arranged for allowing and influencing a fluid flow between the first and second chambers within the damper when the cylinder attachment portion and the piston attachment portion move away from and/or move towards each other.
Description of the Related Art
Such frequency-dependent dampers are well-known for use in automotive engineering. Their aim is to change the damping characteristics as a function of the frequency. More particularly, the aim is to decrease the shock-absorbing characteristics at relatively high frequencies. An example of such a frequency-dependent damper can be found in U.S. Pat. No. 5,129,488. In this case, a part of the fluid moves from the first to the second main chamber via a passage which is (partly) closed by an auxiliary piston during a prolonged movement of the piston rod, as a result of which the damping resistance increases. Such dampers are not capable of achieving other frequency-dependent characteristics which are demanded in certain technical fields. An example thereof are railway applications, in which the damping between the undercarriage of a railway carriage and the upper carriage part mounted on the undercarriage is important for the stability of the carriage during travel of the train. In this case, little damping action is required at low frequencies, while a stiffer damper is required at relatively high frequencies. In addition, there are other technical applications which require a different frequency-dependent characteristic from that described in U.S. Pat. No. 5,129,488. The fluid can be a liquid like, for instance, oil.